Means for controlling the temperature in furnaces and other apparatus



Jan. 18, 1927.

N. H. FREEMAN MEANS FOR CONTROLLING THE TEMPERATURE IN FURNACES ANDOTHER APPARATUS Filed Feb. 5. 1921 Patented Jan. 18, 1927.

UNITED STATES PATENT OFFICE.

NAT HARRIS FREEMAN, OF HOLBORN, LONDON, ENGLAND.

MEANS FOR CONTROLLING THE TEMPERATURE IN FURNACES AND OTHER APPARATUS.

Application filed February 3, 1921, Serial No. 442,195. and in GreatBritain August 21, 1917.

The present invention relates to means for automatically controlling thetemperature in furnaces, ovens, retorts and other apparatus, of the kindin which expansion of air or gas in a vessel, due to increase oftemperature, causes a body of mercury to close an electrical circuitwhich actua-tes means to reduce the temperature, and the main objects ofthe invention are to provide devices of this kind by the use of whichthe furnace or the like may be kept at any desired temperature with veryfine accuracy of control, and also to provide devices for the saidpurpose operable within a large range of temperatures and yet with greator fine accuracy of control where necessary, as for instance when thepredetermined temperature to be maintained is comparatively low.

According to one feature of the present invention, the electricalterminal with which the mercury (:o-acts to make and break the circuitaforesaid is adjustable and the part of the mercury container,?containing the portion of: mercury the upward or downward movement ofwhich closes or opens he aforesaid electrical circuit, is inclined tothe vertical sothat the direction of flow ot the mercury therein is atan angle to its surface. Conveniently, the said part of the mercurycontainer is made adjustable so that the upper surface of the mercurytherein may be more or less inclined relatively to the said direction offlow. By these provisions very fine accuracy of control may be obtainedas the distance the mercury travels under a particular pressure isgreater when the mercury is inclined than when it is vertical and thearrangements for adjustment of the terminal provide for proper initialadjustment of its position and variation of position from time to timeas may be necessary in consequence of variation in the quality of thefuel used. When the inclination of the mercury is adjustable asaforesaid the increase of travel of the mercury may be varied accordingto the temperature to be maintained, the adjustability of the terminaladmitting of variation of its position according to the inclination ofthe mercury. In, this case, therefore, the instrument may be adjusted tooperate with-in a large range of temperatures with very fine accuracy ofcontrol where it is necessary, that is, when the mercury is muchinclined from the vertical to adjust the instrument for comparativelylow temperatures.

In order that the said invention and the manner in which it may becarried out may be clearly understood the said invention is hereinafterparticularly described with reference to the accompanying drawing whichillustrates the preferred embodiment thereof.

Figure 1 is a. diagrammatic side elevation, partly in section, showingone form of controlling means according to the invention; and

Figure 2 is a vertical section, enlarged, showing a detail of theapparatus shown in Figure l.

The mercury container, which is outside the furnace or the like consistsof a tubular part a in an upright fixed portion a the upper part ofwhich tubular part is connected to the end of a tube 7) communieatingwith the air vessel 0, (which is within the furnace or the like) and amovable tubular part a of glass or other electrical. insulatingmaterial. One end of this movable part a is secured in a metal trunniond in the fixed portion a and communicates through passages (Z d (i d inthe trunnion (Z with the lower end of the tubular part a of the mercurycontainer. As shown in Figure 2, the trunnion is in the form of a rotaryplug having in its periphery an annular groove (Z into which the lowerend of the part 0: opens in all positions into which the trunnion may beturned. A radial passage (Z connects the groove (1 with the inner end ofan axial bore-hole d in the trunnion, and the part (1 opens at the outerend of the trunnion into the other end of the bore-hole by Way of asecond radial passage, as shown at d. The trunnion d is slightly conicaland ground into its bearing in the part a? and secured therein by ascrewnut after the man ner of a plug-cock. The angularly adjustableparts are shown in an inclined position in Figure 1, and directedvertically downwardsin Figure 2. It will be seen that the trunnion dconstitutes an adjustable con necting part between the container w andthe tube a Within the part of the adjustable part a of the mercurycontainer above the mercury a therein, an electrical terminal 6 in theelectrical operating circuit is axially arranged, the said terminalbeing the end of awire which passes out of the upper end of the saidadjustable part a and is bent round and secured to a rod f which isslida-bly secured in a. carrier g working on a carrier rod 71 parallelto the said adjustable part. The end of the carrier rod h contiguous tothe trunnion (Z is secured in a metal plate 2' which is carried by thesaid trunnion through the medium of a block of electrical insulatingmaterial 7' secured thereto. The said metal plate 2' also carries ascrew l: with hand wheel I i which screw is engaged with a screw threadin the carrier 9. By turning this screw the position of the carrier 9and consequently the position of the electrical terminal e in themercury container may be very finely adjusted, a coarse adjustmentbeingmade by sliding the rod f to which the outer end of the terminal wire orconductor e is secured, in the carrier 9 in which it is retained afteradjustment by a clamping set screw, not shown. The fixed portion a ofthe mercury container is in the aforesaid electrical circuit andelectrical current passes through it to the mercury when the circuit isclosed. The adjustable part (L2 of the mercury container with the otherparts carried by the trunnion (Z may be moved round by hand in an arefrom a vertical to a horizontal or nearly horizontal position, the partsremaining in theiradjusted position by the friction of the trunnion d inits hearing. The electrical circuit is throughthe part a trunnion cl andmercury a to the terminal 6, when in contact with the mercury, rod fcarrier 9 and 7L and plate 2'. In the circuit is a battery Z andelectromagnet m which, when the circuit is closed by the mercury (icontacting with the terminal 6, is energized and operates the pivotedarmature n. This armature a has on it two metal pins a a located andworking in two mercury cups a a which are in another electrical circuitcomprising a battery 0 and electro-magnet- 7). lVhen the armature nactuated the pins a a are depressed into contact with the mercury in thecups 72 a? and close the second electrical circuit thereby energizingtheelectro-magnet p which actuates a pivoted armature y carrying a valve ordamper 2* which is situated adjacently to the mouth of the gas supplypipe 8 to the furnace so that as the armature q isactuated the valve ordamper r closes or opens the gas supply pipe more or less. The mouth ofthe gas supply pipe 8 and armature g are located in a chamber t to whichthe fuel. is supplied. hen there fore the mercury a is caused to rise inthe part a? of the mercury container, by expansion of the air inthevesselc duev to rise of temperature in the furnace, until the mercurycontacts with the terminal a, the first electrical circuit iscl0sed,.thereby closing the second circuit and operating the damper r toreduce the fuel supply to the furnace. These relay provisions do notconstitute part of the present invention apart from the main featurethereof.

In order to allow attainment of the desired temperature in the firstinstance an adjustable relief valve is provided in the pipe 6 whichvalve is opened or allowed to open while the said temperature is beingattained and when the said temperature is reached the said valve isclosed the purpose icing to prevent undue pressure in the air bulb. Thisfeature however does not con stitute part of the present invention apartfrom the main feature thereof.

By turning the trunnion (Z and parts carried by it more and more fromthe vertical to the horizontal the surface of the mercury (1. in thepart- (19 becomes greater and greater and the distance the mercurytravels under a given increase of pressure is increased the result beinga very accurately acting adjustment of the control.

In cases where no provision for variation of the delicacy of the controlis needed the part (L2 may have a fixed inclined position at any angleto the horizontal according to requirements.

What I claim as my invention and desire to secure by Letters Patentis 1. In a circuit closing device, the combination of a container, anelectrically conducting liquid therein constituting one terminal of anelectric circuit, a tubular trunnion rotatable about its longitudinalaxis and in open communication with the chamber in all positions of thetrunnion, a tube of insulating material carried fluid tight at one endby said trunnion and opening into the'samc, and an electrical contactpiece extending into the other open end of said tube, which contactpiece is normally located above the level of the liquid in saidcontainer and constitutes the other terminal of said circuit.

2. In a circuit closing device, the combination of an uprighttubularmercury container. a horizontal tubular trunnion mounted at the bottomthereof and rotatable about its longitudinal axis, said trunnion havingan annular groove that opens into the said container in all positions ofthe trunnion and is connected to the interior of the trunnion, a glasstube mounted by its lower end on said trunnion and opening fluidtightinto the same, an. electrical terminal in the form of a wireextending endwise into the upper end of said glass tube, and means.carried by said trunnion for adjusting said wire in said tube.

In testimony whereof I tlliili mv signature.

NAT HARRIS FREEMAN.

